This invention relates to a new compound having utility as a luminescent material and more particularly relates to a new hafnium, zirconium phosphate luminescent material excitable by x-ray, ultraviolet, etc. radiation and also relates to a method for producing large single crystalline particles of such material, and to x-ray intensifying screens incorporating such material.
Self-activated hafnium pyrophosphate, zirconium pyrophosphate, and mixed hafnium, zirconium pyrophosphate luminescent materials, which emit in the lower ultraviolet region of the electromagnetic spectrum, are known. For example, U.S. Pat. No. 2,770,749 issued to A. Bril et al discloses a zirconium pyrophosphate phosphor. I. Shidlovsky et al in "Luminescence of Self-Activated Hafnium Pyrophosphate", Abstract #95 of the May, 1974 meeting of the Electrochemical Society, disclose that hafnium pyrophosphate emits in the ultraviolet region more efficiently than zirconium pyrophosphate when excited by photoluminescence and cathodoluminescence. In U.S. Pat. No. 3,941,715, Shidlovsky discloses mixed (Hf,Zr)P.sub.2 O.sub.7 phosphors which emit in the lower ultraviolet region (below about 3,000 Angstroms) when excited by x-rays, cathode rays or visible radiation.
Hafnium phosphate luminescent materials having the formula Hf.sub.3 (PO.sub.4).sub.4 and containing activator elements such as Cu and Eu are disclosed in U.S. Pat. Nos. 3,905,911 and 3,905,912 to J. E. Mathers, and assigned to the present assignee. However, upon excitation by x-rays these materials emit in the visible portion of the spectrum, and are therefore of no utility for x-ray intensifying screen applications requiring ultraviolet emissions.